Ensure bower.json example uses valid JSON

I appreciate this is a minuscule change but it might save people a bit of time - the bower.json example isn't actually valid JSON, which results in a potentially confusing error:
```
bower                       EMALFORMED Failed to read /home/nick/repo/bower.json

Additional error details:
Unexpected token n
```

This PR simply encapsulates the keys in quotes to make the JSON valid.

Apologies about the addition of a newline at EOF; I've submitted this PR via GitHub's web interface. I didn't go anywhere near that last line.